Honestly, I don't tell them about any illness I have as I am sincerely hoping it won't impact on my work.
I will either use annual leave for appointments or work at home on those days if I know the appointments will be short.
Its unlikely my next job will be 9-5 anyway so if I am putting in extra hours, I expect to be able to take them back when I need them.
One job I have applied for is supporting all over the world so I imagine I'll be doing early starts and late nights.
I think that businesses have become much more flexible, particularly with regards to working hours and working from home, this is helped by technology (my work blackberry never stopped flashing at my last job). But its so competitive out there that you have to be careful.
I know I can do an awesome job despite my various medical problems, but the only way I can prove that is by doing it.
I've been regularly working at home for years since I developed IBS which made commuting very difficult. I get a lot more done at home anyway!!!!